1. Field of the Invention
The present invention relates to a thin film transistor substrate and a method of fabricating the same, and more particularly, to a thin film transistor substrate and a method of fabricating the same in which the number of processes is reduced.
2. Discussion of the Related Art
A liquid crystal display device displays an image by adjusting light transmittance of liquid crystals having dielectric anisotropy using an electric field. Such a liquid crystal display device includes a liquid crystal display panel including a thin film transistor substrate and a color filter substrate bonded to each other opposite each other, a backlight unit irradiating light to the liquid crystal display panel, and a driving circuit unit to drive the liquid crystal display panel.
The thin film transistor substrate includes gate lines and data lines formed on a lower substrate so as to intersect each other under the condition a gate insulating film is interposed between the gate lines and the data lines, thin film transistors (TFTs) formed at the intersections, pixel electrodes connected to drain electrodes of the TFTs through contact holes, and a lower alignment film applied thereto.
The color filter substrate includes color filters to implement colors, a black matrix to prevent light leakage, a common electrode forming a vertical electric field with the pixel electrodes, and an upper alignment film applied thereto to align liquid crystals.
The liquid crystal display panel may be formed in a twisted-nematic (TN) mode in which electrodes are respectively installed on two substrates and liquid crystal directors are aligned to be twisted at an angle of 90° and are driven by applying voltage to the electrodes. Further, an in-plane switching (IPS) mode in which two electrodes are formed on one substrate and liquid crystal directors are adjusted by a horizontal electric field generated between the two electrodes, or a fringe field switching (FFS) mode in which two electrodes are formed of transparent conductors and an interval between the two electrodes is reduced so that liquid crystal molecules are operated by a fringe field formed between the two electrodes may be used.
Here, a method of fabricating an FFS mode thin film transistor substrate includes a process of forming gate electrodes using a first mask, a process of forming a semiconductor pattern using a second mask, a process of forming source/drain electrodes using a third mask, a process of forming a first passivation film including pixel contact holes and contact holes of pad areas using a fourth mask, a process of forming pixel electrodes using a fifth mask, a process of forming a second passivation film including pixel contact holes and contact holes of pad areas using a sixth mask, and a process of forming a common electrode on the second passivation film using a seventh mask. The method of fabricating the FFS mode thin film transistor substrate requires at least seven mask processes, as described above, and may thus cause increase in process costs and process time.